Parallel lines are lines that share the same slope (steepness) and therefore never intersect. A transversal occurs when a set of parallel lines are crossed by another line. All of the angles formed by a transversal are called interior angles and angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°) and are called corresponding angles. Alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°) and all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other. Same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°).

The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 39° - 36° = 105°

To solve this equation, isolate the variable for which you are solving (c) on one side of the equation and put everything else on the other side.

6c - z = -c - 5z - 4
6c = -c - 5z - 4 + z
6c + c = -5z - 4 + z
7c = -4z - 4
c = \( \frac{-4z - 4}{7} \)
c = \( \frac{-4z}{7} \) + \( \frac{-4}{7} \)
c = -\(\frac{4}{7}\)z - \(\frac{4}{7}\)

You can only add or subtract monomials that have the same variable and the same exponent. For example, 2a + 4a = 6a and 4a² - a² = 3a² but 2a + 4b and 7a - 3b cannot be combined. However, you can multiply and divide monomials with unlike terms. For example, 2a x 6b = 12ab.

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the < sign and the answer on the other.

9x - 3 < 6 - 7x
9x < 6 - 7x + 3
9x + 7x < 6 + 3
16x < 9
x < \( \frac{9}{16} \)
x < \(\frac{9}{16}\)